The royals were seated in a box high above the crowd of 20,000 invited guests to enjoy music from the 60 years of the Queen's reign. Many of the attendees waved Union Jack flags – Kate included!

The Duchess – in an Alexander McQueen jacket and a dress from Whistles – sat between Prince William and Beatrice. The young royals were just behind Prince Charles and his wife Camilla as they all listened to tunes from the likes of Paul McCartney, Tom Jones and Stevie Wonder.

Hundreds of thousands jammed the nearby streets and parks to get a listen, as well. Despite the fanfare, the concert was overshadowed by news earlier Monday that Prince Philip had been rushed to the hospital as a precautionary measure after developing a bladder infection.

But the show must go on, and Robbie Williams opened the concert with a rousing rendition of "Let Me Entertain You," which the royals seemed to enjoy, waving their flags in response. Will.i.am and Jessie J followed with "I Gotta Feeling."

At about 9 p.m., comedian Lenny Henry invited the crowd to welcome the Queen to the royal box. She wore a gold cocktail dress adorned with Swarovski crystals and was escorted to her seat by Charles and Camilla.

'Thank you, Mummy'

Charles led the country in thanking the people who made the concert happen. But most importantly he thanked the woman he playfully called "mummy."

"As a nation this is our opportunity to thank you and my father for always being there for us, for inspiring us with selfless duty and service and making us proud to be British," said the prince.

Acknowledging that his father couldn't be present, Charles said, "The only sad thing about this evening is that my father could not be here with us because he's unfortunately he's taken unwell. But ladies and gentlemen, if we all shout loud enough he might just hear us."

Charles also said he was happy it didn't rain for the Queen's big day. "Thank god the weather turned out. The reason, of course, was because I didn't do the forecast," he joked in a reference to his recent turn in front of the cameras doing the weather for the BBC.

McCartney speaking about the guest of honor, said, "The main thing is for me ... is the human aspect. You never realize because we always see them on stamps and money … I have always found her to be very warm and very nice."

Organizer Gary Barlow told ITV News of the event: "Buckingham Palace itself is the backdrop to the event, it's the most historic backdrop in the world. We tried to pick artists from right across her reign, from the 50s and 60s right up to the modern day."

The official jubilee tune "Sing" penned by Barlow and Andrew Lloyd Webber was also performed. In the recorded version of the song Prince Harry played the tamborine.